The present invention relates to self-adhesive labels and to a method of producing self-adhesive labels. In particular, the present invention relates to self-adhesive labels of multilaminar construction in which the label incorporates a booklet or folded sheet so as to provide a large surface area for carrying printed information which is greater than the surface area of the footprint of the label. The labels of the present invention have particular application in the labelling of pharmaceutical products.
A variety of so-called leaflet labels or booklet labels are known in the art and a typical label construction is disclosed in U.S. Pat. No. 5,399,403 in the name of David J Instance. It is well known for the folded leaflet or booklet to be overlaminated with a self-adhesive transparent plastics layer. The overlaminate provides durability to the label against inadvertent damage or tearing and also improves the aesthetic appearance of the label. Furthermore, the overlaminate can provide a structural part of the label to enable the leaflet or booklet label to be opened from a closed configuration by pulling the overlaminate away from a surface of a product, such as a pharmaceutical container, which is labelled to enable the leaflet or booklet to be read by a user. In some labels, the overlaminate can be re-adhered to the product to return the label to its closed configuration. Typical plastics materials for use as the overlaminate include oriented polypropylene carrying a pressure-sensitive adhesive on its rear surface.
U.S. Pat. No. 4,529,229 discloses a self-adhesive label in which an adhesive strip is provided to retain a folded strip in its folded configuration by being adhered to a top panel and an underlying panel of the strip.
When pharmaceutical products are labelled, it is often necessary for the label to be printed with specific information such as a lot or batch code and an expiry date. Such printing is generally achieved by providing a generic printed label for a particular pharmaceutical product and then overprinting a series of the labels with the required batch or lot code and expiry date.
A technical problem exists in the art in that there is a need to provide on overlaminated leaflet or booklet labels an overprint area and in particular an overprint area which is suitable for being printed with high quality alphanumeric printing devices suitable for printing batch codes, expiry dates and the like. There is also a need in the art for such overlaminated labels, particularly for pharmaceutical products, to be overprinted with bar codes which contain information relating to the overprinted batch codes, expiry dates, etc. and act as a security feature which can be scanned automatically to check that the required overprinting has been effected. The bar code needs to be small in area yet accurately printed in order to be machine readable at high speeds.
When information is overprinted onto paper, i.e. when a non-overlaminated leaflet or booklet label is being printed, ink is printed onto the paper surface of the label and then a laser is employed either to vaporise some of the ink so as to leave white lettering surrounded by the ink or to bum the lettering into the surface of the paper. The present inventor has attempted to replicate this laser printing process onto a plastics overlaminate, in particular an oriented polypropylene self-adhesive laminate. However, following laser treatment the appearance of the printing is poor because the laminate tends to have a bubble effect imparted thereto by the laser, which the present inventor believes results from vapours being emitted from the paper surface and thermal distortion of the plastics laminate. In addition, it is believed that the overlaminate absorbs some of the energy from the laser which may require the utilisation of a relatively powerful laser, or a longer burn time, which may in turn exacerbate the bubbling problem.
The present inventor has also attempted to overprint onto a plastics overlaminate by using a thermal transfer printer. Such thermal transfer printers use a multi-element print head with a large number of tiny heating elements that can be turned on and off in a desired pattern or configuration under computer control so as to print selected alphanumeric characters. A ribbon is pressed between the print head and the substrate to be printed and when the print head elements are turned on so as to become heated, the elements soften the coating on the surface of the ribbon in contact with the substrate allowing the coating to stick to the substrate as a pattern of dots. The desired alphanumeric symbols to be printed are of course controlled by selectively activating the desired pattern of heating elements. The present inventor has discovered that the plastics overlaminate surface tends not to be receptive to some thermal transfer coatings.
There is also a desire to overprint a plastics overlaminate by means of wet printing. In wet printing a liquid vehicle of a wet printing ink dries by absorption into the printed substrate. This is not possible with a plastics overlaminate because the vehicle cannot absorb thereinto, leading to smudging of the printed image.
The present invention aims at least partially to solve these problems of the prior art.
It is known to provide a two-component leaflet or booklet label in which a leaflet or booklet is overlaminated with a self-adhesive transparent plastics layer which is adhered on opposed sides of the leaflet or booklet to a backing of release material (or release liner), such as silicone-coated paper. A typical label having such a construction is disclosed in FIG. 4 of U.S. Pat. No. 5,399,403. The opposed laminate portions on opposed sides of the booklet or leaflet constitute leading or trailing edges of the label in the direction of the length of the liner web of release backing material. The self-adhesive leaflet or booklet labels are automatically applied to products to be labelled by providing a reel of the labels carried in succession on the web of release backing material and the reel is unwound and the backing of release material is pulled back over a peel plate of the label applicator whereby the leading edge of the forwardly moving label is fed off from the release backing material onto the product. When the leading element of the label to be dispensed consists of a laminate flap, i.e. simply the overlaminate which is initially adhered to the backing of release material, the flexibility of the laminate and its inherent lack of stiffness tends to make it difficult to ensure that the leading edge of the label defined by the laminate breaks away from the liner of release backing material at the peel plate. Accordingly, it is known in the art, in order to provide sufficient stiffness to the laminate to enable the leaflet or booklet label to be dispensed acceptably by the label applicator, for a relatively thick laminate to be employed, for example a laminate 0.002 inches (0.0508 mm) thick, which is greater than the thickness required both for protection of the label and to ensure that following die-cutting of the labels the laminate is sufficient strong to constitute a matrix web which pulls waste cut away portions of the labels away from the release material.
It is a further object of the present invention at least partially to solve this problem of the prior art, and in particular to provide sufficient stiffness to the leading edge of a label to enable it to be dispensed by a label applicator without requiring an excessively thick self-adhesive transparent plastics laminate.
It is yet a further object of the present invention to provide an overlaminated label having sufficient thickness whereby no modifications to a standard label applicator are required.
Known leaflet and booklet labels can suffer from the disadvantage that when several versions of the same label construction corresponding to slight variations in the product to be labelled are required, it is necessary to have an entirely separate printed leaflet or booklet for each version of the label. For example, a pharmaceutical product may require two versions of substantially the same label, one version for each particular strength of the same pharmaceutical product and for agrochemicals, two versions of the same label may be required for different bottle sizes, e.g. 1 liter and 5 liters. The requirement to manufacture a number of substantially the same labels having slight variations relating to the differences in the products can be relatively inefficient to manufacture, particularly for short manufacturing runs for the labels, because this requires the folded leaflet or booklet parts to be manufactured to order or held in stock for each label version.
It is a further object of the present invention to provide lower cost leaflet labels or booklet labels, particularly for short run multiple brand name versions of the same label.